[joern]

Hi,

I'm searching for the mathematical basics of the GAMG Solver.
In my literature i only find GMG and AMG. I want to know how the GAMG works and whats the difference to GMG and AMG.


Joern

[mattijs]

GAMG is geometric/algebraic MG. Instead of the agglomeration being calculated from the matrix coefficients (and thus differ every 'solve') this one can use an agglomeration based on geometry (which is usually constant and can be cached).

See the 1.4 release notes. http://www.opencfd.co.uk/openfoam/doc/ReleaseNotes-1.4

[braennstroem]

Hi Mattijs,

how can I adjust the agglomaration? Is setting cacheAgglomeration to true enough for the geometric and setting it to false ennough for the algebraic version?

Thanks!
Fabian

[mattijs]

enter an invalid name for the agglomeration and you'll see the possible agglomeration methods. You can make your own one. Look e.g. at pairGAMGAgglomeration.H. Cache the agglomeration if you don't mind the extra storage and it does not change.

[braennstroem]

Ah, I see, the choices are algebraicPair and
faceAreaPair; I assume that one would mostly use the faceAreaPair as long as there is no mesh motion and no automatic mesh adaption!?

Thanks!
Fabian

[braennstroem]

Hi,

I wonder, if there is an option to write out the agglomerated coarse mesh for every level?

Thanks in advance!
Fabian

[braennstroem]

Hi,

me again...
do you have a hint, if the use of an agglomerated coarse mesh is the good approach to get a coarse surface and volume mesh!? I would like to use a real coarse mesh for thermal calculations of a room divided in a couple of regions.

Fabian